The invention relates to folding machines.
A folding machine is described in U.K. Patent Specification No. 985,732 which comprises a pair of folding members mounted for pivotal movement in opposed directions about a common pivot axis from a rest position in which the upper surfaces of the forming members are co-planar to a folding position in which each of said upper surfaces are inclined to each other and a holding tool located above said axis and moveable into contact with a sheet metal or other workpiece laid across the upper surfaces of the folding members in their rest position to provide a stationary fold guide during the folding operation.
The folding machine can be used with a small radius holding tool in which case the pivot axis of the forming members almost coincides with the edge of the hold down tool. The upper surfaces of the folding members are then little more than the thickness of the workpiece away from the pivot axis so that during a bending operation there is very little movement of the position of the folding members.
However, when it is intended to produce a fold other than a simple angle, for example a fold of a finite larger radius, the holding tool should be of a shape to correspond to the required fold and the distance of the pivot axis from the surface of the folding members may be substantial. In the example of a fold of finite radius, the distance from the folding members to the pivot axis should be equal to the required radius of the fold plus the thickness of the material to be folded. In this kind of situation, a substantial gap opens up between the folding members during the folding operation and this can be detrimental to the function of the machine. For some folds the workpiece can drop down between the folding members. A thin workpiece can spring out into the gap and be pinched or distorted by the return stroke of the folding members.
An object of the present invention is to provide an improved folding machine in which these disadvantages are alleviated.